Guest

Egpws Warning In An Engine Out

Sat May 11, 2002 4:41 am

I was shooting the breeze with an airline pilot friend on various aviation topics and the subject came up on what should a pilot do.

The scenario is that you operate from a mountainous airport with rising terrain at end of runway. The weather is lousy (low Viz) and after V1 you have an engine failure. You took off and on your way to 1000 ft. The EOSID is designed to keep the a/c cleared of terrain but not enough to assure that an EGPWS (or TAWS) warning does not happen (it would be a false warning in this case). Due to the low viz, you can't see to make turns to avoid terrain.

It is conceivable that if the pilot follows the EGPWS warning and pull up, after the initial altitude gain, the aircraft will actually be below the Engine Out profile and could get in trouble with not being able to clear the next hill. I was told that airline policy requires pilots to follow an EOSID and EGPWS Warning.

I'd appreciate your thoughts on this topic.

Regards,
Nut
 
Guest

RE: Egpws Warning In An Engine Out

Sat May 11, 2002 5:30 am

Nut,
It's called situational awareness. This would be a scenario where the pilot's judgement and experience would make or break the day. I'm sure that in addition to requiring company pilots to adhere to the SID and follow any EGPWS warnings, there is also a policy against flying into a mountain. Remember, it's the unexpected EGPWS warnings that are life savers. The flight crew should have thought this possibility through prior to takeoff and figured out that if an engine failure occured, there might be the possibility of a false warning and fly accordingly. (One nice thing about EGPWS is that you can actually see the terrain representation on the MFD, so in a limited way you still can see and avoid.) BTW, this is actually a scenario that we are faced with when we takeoff to the north here at LMT.
Jetguy
 
ewr757
Posts: 354
Joined: Mon Apr 03, 2000 8:47 am

RE: Egpws Warning In An Engine Out

Sat May 11, 2002 9:33 pm



All airports that have terrain considerations will require a special engine out procedure (i.e. non standard profile) for said airport. It is mandatory they are briefed prior to each departure. These profiles are listed as special addendums to our Jepp pages.

In theory, these special profiles should not give you an EGPWS warning after departure if flown correctly.

 
Guest

RE: Egpws Warning In An Engine Out

Sun May 12, 2002 8:26 am

Perhaps I should have taken more time with my original answer, but oh well, let me clarify a couple of points…

EWR757 made the following comments: “All airports that have terrain considerations will require a special engine out procedure (i.e. non standard profile) for said airport. It is mandatory they are briefed prior to each departure. These profiles are listed as special addendums to our Jepp pages. In theory, these special profiles should not give you an EGPWS warning after departure if flown correctly.”

That is absolutely correct. For you airline guys, airport analysis will have a special departure procedure, if the required climb gradient is too steep, that will give a route that will guarantee obstacle clearance. Even though the Takeoff & Obstacle DP on the back of the Jepp says to climb straight out or make a left or right turn, the Special DP might be an opposite turn. Please keep in mind that the airport analysis is specific to each aircraft and takes into account a multitude of factors, like single engine service ceiling, etc.

For us non-airline types, we’ve got to pretty much fend for ourselves when operating at airports whose departure procedures require something other that the standard TERPS gradients. We usually have no choice but to comply with the published SID or Takeoff & Obstacle Procedure. They can be quite complex and convoluted, but it is imperative that they be flown precisely if you want to keep from putting your nose into the dirt when departing these airports under IFR conditions. Typically, our only option is to reduce our weight until we are light enough to meet the published minimum climb gradient.

As an example, departing IFR out of Aspen, CO (KASE) on RW33 via the Aspen Two Departure requires a climb gradient of 950’ /NM to 12,000’ MSL. This departure is basically a slight right turn after takeoff followed by a straight out climb. The Lindz Four Departure is somewhat more manageable with a required climb gradient of “just” 460’/NM to 14,000’ MSL. However, this procedure is pretty complex, involving the interception of an offset back course LDA then the interception of a radial off of the DBL VOR. The published Takeoff & Obstacle DP is similar to the Lindz Four Departure. As far as departing from RW15, forget it. Only the Space Shuttle would have the climb gradient necessary.

Any of these procedures has the possibity of setting off the EGPWS if you only achieved the minimum clearance provided by the TERPS procedures. Speaking of TERPS, those of us operating in the U.S., Canada, Mexico, and (I believe) Chile are fortunate, TERPS takes into account the loss of performance as the result of an engine failure when developing the departure procedures. As far as the rest of the world goes, ICAO does not consider engine failure or any other aircraft emergency after V1 in the construction of departure procedures. Again, you international airline guys have Airport Analysis to bail you out, the rest of us have to work it out for ourselves.

Jetguy
 
Guest

RE: Egpws Warning In An Engine Out

Tue May 14, 2002 2:59 am

EWR757:"In theory, these special profiles should not give you an EGPWS warning after departure if flown correctly. "

You are right that in theory the profiles should not give you EGPWS. In reality, however, since most of the performance guys who does the charts and the profiles can't even spell EGPWS, let alone knowing what the warning criterias are...these profiles are NOT designed to guarantee free of EGPWS warnings because they aren't correllated with EGPWS systems at all. Somewhere in the Honeywell EGPWS web page, this very issue is mentioned...Due to airlines' pressure, Honeywell is considering changing EGPWS design to not ever warn during an engine-out.

What JetGuy stated for business jets, I think, is equally applicable to airliners, too.

Regards,
Nut

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